This invention relates to the process of injecting medicament by means of a disposable, single use, filled or pre-filled, ampule utilizing an impact impulse injector that horizontally to perpendicularly delivers intradermal, (ID), subcutaneous (SUB-Q) and intramuscular (IM) injection in a human or animal tissue by means of a thin high pressure liquid jet stream of sufficient velocity to penetrate the tissue of the recipient. The injector deposits the medicament intradermally, or subcutaneously, or intramuscularly, utilizing a single use, disposable, medicament ampule that is designed to provide interfaces to the activation device, allowing easy installation by hand, and providing exact positioning and sealing to the activation device structure. The ampule further contains features that induce a vacuum to stretch the skin, keeping the skin precisely aligned with the jet orifice for the short duration of the injection. The ampule's orifice has different offset variations for ID, SUB-Q or IM injections. Ampules and injectors may also be adjusted for variations in medicament viscosity as required by various classes of medicaments. The manually operated or pneumatically activation device provides the interface features for mounting the ampule, and the features necessary for the impulse force to horizontally to vertically inject the medicament, as the activation process is performed. In addition, the activation device provides safety interlock features which prevent the impulse force from being inadvertently activated, except when the ampule is properly interfaced with the skin surface. The injector provides the operator with a comfortable, light weight device that allows the operator to quickly and easily load an ampule, properly position the ampule on the skin surface, activate the impulse force, injecting the medicament and resetting the activation device.
In this invention, a needle-free ampule discharges a pre-measured quantity of fluid medicament in a thin jet at a sufficient velocity to horizontally to vertically penetrate the tissue of both human and animal to be treated or vaccinated.
This invention utilizes a single-use, disposable medicament ampule which uses a vacuum to stretch and properly hold the skin for injecting into the tissue, and a manually or pneumatically operated activation injector device. The ampule and the injector are truly unique designs. Although they are constructed with materials presently being used in the medical industry, they were designed to minimize effort, be easy to handle and operate. The size and shape selected also minimize weight. The age, size of hands, hand strength, skin type and thickness, as well as visibility of operations, were very important considerations.
Present state of the art that attempts to inject medications intradermally have met with only limited success due to the inherent difficulty associated with accurate positioning of the skin relative to the injector jet opening and the lack of precise control of the jet pressure vs. skin penetration when the injection is performed normal to the skin surface. In addition, present systems lack precise control and repeatability of the injection jet velocity due to mechanical equipment tolerance variations within the pressure/force generators utilized. Some present devices present safety concerns due to the lack of safety interlocks to prevent the device from being activated when not in proper contact with the skin, and catastrophic failures have been observed in the injector bodies in part caused by the lack of pressure control inherent in the device designs.
Needleless injectors have been used as an alternative to hypodermic needle type injectors for delivering drugs, vaccines, local anaesthetics and other fluids into the human or animal tissue. The medicament is discharged in at high velocity after first penetrating the epidermis and thereafter be deposited in the tissues of the subject. An alternative method is to press the discharge nozzle onto the skin and force the fluid at very high pressure through the epidermis.
Prior art devices generally employ spring loaded piston pumps to generate injection pressure to withdraw fluid from a reservoir. At the end of the piston stroke, the piston is disengaged from the retracting mechanism and pressures the fluid from the delivery nozzle. In some devices the fluid is contained in an adjacent container or vessel within the device and the fluid is fed into the nozzle under pressure and discharged under pressure by the delivery nozzle, In other prior art devices the piston is driven on the discharge stroke by gas or electric motor instead of a spring. In most of these devices the discharge orifice is placed firmly on the skin to make contact of the nozzle to the epidermis, and to achieve suitable contact, the orifice is pressed firmly into the epidermis normal to the surface. This is done to stretch the epidermis at point of contact and increase the ability of the injection to penetrate the stretched tissue at point of contact. However, the pressing of the orifice into the epidermis is a variable dependent on the devicc's operator, and the ability of the recipients to tolerate the device being pressed against their anatomy.
Typically, the use of existing devices results in loss of medicament at the nozzle entry point, poor injections on account of recipient's movements, and receipt of the injection at an angle that does not penetrate or penetrates too much for placement and dispersal of the medicament at the correct depth and layer of tissue. In addition, premature operations are common, as well as relative movement between the epidermis and orifice can cause tearing of the skin during injection, resulting in pain and poor transfer of the medicament to the recipient. In other instances, the epidermis will deform away from the orifice and the injection fluid will leak away from the point of entry. At other times, the devices attempt to stretch the epidermis by deforming over the discharge orifice. In all of these conditions, the success of the injection procedure depends and rests on the ability of the applier to consistently perform, using the device to get an acceptable discharge and penetration of the epidermis.
Various methods have been proposed to overcome these problems such as powered injectors, sensing and control devices to enhance their performance, including compressed gas cylinder and electrical injectors, often heavy and unwieldy, and encombered with variations in gas supply, pressure, leakage.
The need for medicament supply and personnel skill have produced a problem for using these devices, precisely measuring and control of the quantity of medicament administered and ensuring that the injector delivers the correct amount of medicament into the proper tissue.
The following patents addressed these known problems and proposed some methods, as follows:
U.S. Pat. No. 3,859,996, Mizzy, discloses a controlled leak method to ensure that the injector orifice is placed correctly at the required pressure on the subject's skin at the corrrect normal to the skin attitude. When placement conditions are met, controlled leak is sealed off by contact pressure on the subject's skin, the pressure within the injector control circuit rises until a pressure sensitive pilot valve opens to admit high pressure gas to drive the piston and inject the medicament. This use of valving and pressure gas does not apply to the present invention.
WO Patent 82/02835. Cohen and Ep-A-347190, Finger, discloses a method to improve the seal between the orifice and the skin and prevent relative movement between each. This method is to employ a vacuum device to suck the epidermis directly and firmly onto the discharge orifice. The discharge orifice is positioned normal to the skin surface in order to suck the epidermis into the orifice. This method for injection of the medicament into the skin and the injector mechanism are different and do not apply to the present invention because of its unique ampule design.
U.S. Pat. No. 3,859,996, Mizzy, discloses a pressure sensitive sleeve on the injector which is placed on the subject, whereby operation of the injector is prevented from operating until the correct contact pressure between orifice and the skin is achieved. The basic aim is to stretch the epidermis over the discharge orifice and apply the pressurized medicament at a rate which is higher than the epidermis will deform away from the orifice. This method of stretching the skin on to the orifice, together with the arrangements of the mechanism are totally different from the present invention and, consequently, do not apply.
U.S. Pat. No. 5,480,381, T. Weston, discloses a means of pressuring the medicament at a sufficiently high rate to pierce the epidermis before it has time to deform away from the orifice. In addition, the device directly senses that the pressure of the discharge orifice on the subject's epidermis is at a predetermined value to permit operation of the injector. The device is based on a cam and cam follower mechanism for mechanical sequencing, and contains a chamber provided with a liquid outlet for expelling the liquid, and an impact member, to dispell the liquid. The sequencing and cam operation driven by an electric motor gear-box, cam action sequencing and adjustable pressure sensing do not apply to the present invention.
U.S. Pat. No. 5,891,086, T. Weston, describes a needleless injector that contains a chamber that is pre-filled with a pressurized gas which exerts a constant force on an impact member in order to strike components of a cartridge and expulse a dose of medicament. This device contains an adjustment knob which sets the dose and the impact gap, and uses direct contact pressure sensing to initiate the injection. This use of contact pressure sensing, the need for constant adjustment and the use of pressurized gas to implement the injection process do not apply to the present invention.